This application claims the benefit of Japanese Application 2001-100,954, filed Mar. 30, 2001, the entirety of which is incorporated herein by reference.
The present invention relates to an optical system of a display.
The present applicant has proposed a display element constituted of a rectangular light conducting plate introduced with light and a panel portion provided to oppose to one plate surface of the light conducting plate. The panel portion includes a driving part arranged with actuator parts each corresponding to a plurality of pixels so as to control displacement motions of the actuator parts in the contacting/separating directions to/from the light conducting plate correspondingly to attributions of input image signals, thereby controlling leaked light-beams in predetermined regions of the light conducting plate, to thereby cause the light conducting plate to display an image corresponding to the image signals (see JP-A-7-287176 [287176/1995] and JP-A-11-194723 [194723/1999]). Hereinafter, the display element having such a constitution shall be called a xe2x80x9cdisplay element relating to the present invention.xe2x80x9d
The display element relating to the present invention basically eliminates the necessity of an end-sealing structure such as a liquid crystal display or plasma display, thereby allowing to adopt a divided panel structure and to relatively readily deal with a large-sized thin panel. Further, the display element relating to the present invention is of a direct-viewing type, thereby enabling a higher contrast, rare discoloration, even under influence of the outdoor daylight, and a more excellent viewing angle even compared with a CRT.
It is therefore an object of the present invention to provide a novel optical system preferable to the display element relating to the present invention.
To achieve the above object, the present invention provides an optical system of a display, the display being constituted of: a light conducting plate introduced with light; and a panel portion provided to oppose to one plate surface of the light conducting plate; the panel portion including a driving part arranged with actuator parts each corresponding to a plurality of pixels so as to control displacement motions of the actuator parts in the contacting/separating directions to/from the light conducting plate correspondingly to attributions of inputted image signals, thereby controlling leaked light-beams in predetermined regions of the light conducting plate, to thereby cause the light conducting plate to display an image corresponding to the image signals. The optical system of the display is constituted of the light conducting plate, at least one light source arranged to oppose to one plate surface or one side surface, of the light conducting plate, and a reflector for surrounding the light source in cooperation with the one plate surface or the one side surface of the light conducting plate, the reflector having a reflecting surface for reflecting light-beams from the light source.
According to the present invention, the light conducting plate is introduced with not only direct light-beams from the light source but also light-beams reflected by the reflector, thereby allowing to relatively increase the ratio of the introduced light-beams into the light conducting plate relative to the exiting light-beams from the light source. As a result, even when those exiting light-beams from the light source are relatively weak, it is possible to fill light-beams into the light conducting plate, to thereby preferably constitute the optical system of the display.
Preferably, the panel portion is provided with display elements having predetermined number of pixels arranged on the one plate surface of the light conducting plate, and the optical system of the display further comprises a frame for surrounding an outer periphery of the panel portion. By virtue of such a frame, it becomes possible to position the panel portion upon adhering the same, and to avoid the light leakage at the periphery of the panel portion. The frame exemplarily has a light absorbing or light reflecting surface.
Preferably, the light conducting plate is rectangular or has a rectangular displaying area and the light conducting plate has a thickness of more than 0.01 and less than 0.1 times of the diagonal length of the light conducting plate or of the displaying area thereof. This facilitates those light-beams introduced into the one side surface of the light conducting plate to straightly advance up to the opposite side surface.
In order to improve the luminance characteristic of the display, it is preferable that the light source comprises two or more pieces of light sources, that the light sources are arranged at predetermined intervals therebetween along the one side surface of the light conducting plate and that the predetermined interval is not more than 0.05 times of the shortest distance between an outer periphery of the panel portion and the one side surface of the light conducting plate.
In order to correct color temperature, it is possible to further provide a color-temperature correction light source arranged for the one plate surface or one side surface of the light conducting plate. In this case, the reflector exemplarily accommodates therein 11 pieces of white light sources and one piece of blue light source. Further, it is possible to provide a color-temperature correction light-permeating plate or film arranged for the reflecting surface of the reflector or for the one plate surface or one side surface of the light conducting plate.
In order to improve the ratio of light-beams to be introduced into the light conducting plate and the ventilation, i.e., heat dissipation, the reflector preferably has a profile in an outwardly convexed shape formed by straight lines, continuous curved lines, or a combination thereof. More preferably, the space surrounded by the profile of the reflector and the one plate surface or one side surface of the light conducting plate has those maximum lengths which are not more than 3 times of the thickness of the light conducting plate, in both of the direction parallel to the one plate surface of the light conducting plate and the direction parallel to the one side surface of the light conducting plate.
In order to improve the luminance characteristic of the display, it is possible that the sum of sectional areas of light sources covered by the reflector is not more than 60% of a sectional area of a space surrounded by a profile of the reflector and the one plate surface or one side surface of the light conducting plate.
It is possible to provide a further reflector for defining another space in cooperation with a side surface of the light conducting plate, other than the one plate surface or one side surface of the light conducting plate, the further reflector having a reflecting surface for reflecting light-beams from the light source. In this case, those light-beams emitted from the other side surface are reflected by the further reflector and again introduced into the other side surface of the light conducting plate.
In order to improve the ratio of light-beams to be introduced into the light conducting plate and the ventilation, i.e., heat dissipation, the further reflector preferably has a profile in an outwardly convexed shape formed by straight lines, continuous curved lines, or a combination thereof. More preferably, the space surrounded by the profile of the additional reflector and the one plate surface or one side surface of the light conducting plate has those maximum lengths which are not more than 3.0 times of the thickness of the light conducting plate in the direction parallel to the one plate surface of the light conducting plate and 3.0 times of the thickness of the light conducting plate in the direction parallel to the one side surface of the light conducting plate, respectively.
The luminance uniformity of the display becomes excellent when there are constituted a first light-source group comprising not less than two light sources and a second light-source group comprising light sources in number less than the number of light sources of the first light-source group. The light sources of the first light-source group are arranged along one side surface of the light conducting plate, at predetermined intervals between adjacent ones of the light sources of the first light-source group. The light sources of the second light-source group are arranged along the first light-source group, at predetermined intervals between the light sources of the second light-source group and adjacent ones of the light sources of the first light-source group and at predetermined intervals between adjacent ones of the light sources of the second light-source group.
The luminance uniformity of the display also becomes excellent, when there are constituted a light-source group comprising a plurality of light sources.
The light sources are arranged along the reflecting surface of the reflector, at predetermined intervals between adjacent ones of the light sources. The light-source group includes a first light source and a second light source of the light sources, the first light source and the second light source being closest to one side surface of the light conducting plate. The optical system further comprises an additional light source arranged at an intermediate position of the first light source and the second light source.